A request re. "Can you see stars in the daytime on earth?"

[AstroBrant]

I may be ruffling some feathers with this, but I'm trusting that most of the members have pretty thick skins.

I keep seeing that argument from our side in discussions regarding the visibility of stars in space. I'd like to see people abandon it. The argument is subject to legitimate criticism which hoax nuts just love to derail your other good points with. A hoax nut would legitimately say,

"Apples and oranges. The bright atmosphere is why we can't see stars during the day. In the old days, they used to think that you could get in the bottom of a well, look straight up, and see stars in daytime like you would at night. But now we know this is not true. You wouldn't see stars, no matter how dark-adapted your eyes get. It's not the same as space."

Now we have to backpedal. Not a good option when dealing with these kinds of people.

I have a great deal of respect for some of the people I have seen using this expedient but ineffective argument, so please, don't take offense. Many of them know much more about Apollo than I do, but I think on this point we can do better. The correct position should be to stick with the optical reasons why we don't see stars when there are bright objects in our field of view. The stadium and parking lot lights at nighttime argument is okay. I've begun pointing out how difficult it is to see more than a couple of the brightest stars and planets out of your car window at night, with just the weak dome light on.

Similarly, I have seen some Apollo defenders say, "Stand in the shadow of a building during the daytime. Are you completely dark?"
Again, invalid. The sky lights you up in a way that would not happen on the moon.

My apologies if I've put anybody off.

[ka9q]

I don't see anything wrong with that. I agree, we have so many sound arguments that we don't need to resort to any that aren't bulletproof.

[Bob B.]

People are making that argument?  I don't think I've seen it, or at least I haven't noticed.  I typically see arguments like the following.

The correct position should be to stick with the optical reasons why we don't see stars when there are bright objects in our field of view. The stadium and parking lot lights at nighttime argument is okay.

[Luckmeister]

I've discussed this with local HB's and I didn't have to backpedal. In daytime on Earth, scattering of sunlight in the atmosphere washes out the stars plus the eyes are not dark-adapted.

On the Moon, reflected sunlight makes dark-adapting difficult and the astronauts were too busy to be stargazing even if they bothered to shield their eyes enough. In the ISS, interior lights will prevent dark-adapting. What's wrong with telling them that?

Astronauts can usually shield their eyes (looking through a scope for example) to dark-adapt well enough to see stars if they really want to. Most of the time they don't bother because the stars don't look much different from on Earth. HB's think astronauts would be mesmerized by the incredible view of stars in space. Nope -- it's not that incredible.

[raven]

It's also worth looking at the design of the space suit.  Not only did it force them into a rather hunched posture, but the outer helmet assembly also blocked the upper field of view significantly. They would have a had to really crane their whole body back to look up at enough of an angle to block the lunar surface from sight, which would risk having them fall on their ass with the weight and mass of their PLSS 'backpack'. I believe at least one astronaut did it, but it wasn't something easy to do. If the A7L suits had had a design more like the Russian Orlan, with its nifty porthole in the helmet, it would be much easier, but it's easy to see why they didn't. They came to study the moon. The stars were not a priority for Mark 1 Eyeball Astronomy on Apollo.

[onebigmonkey]

If memory serves that is amply illustrated during Apollo 17 and the arching of the back required to capture astronaut, Earth and flag in one shot.

[Echnaton]

There is no real "our side" vs "their side."  Hoax believers are notoriously disjointed, presenting idiosyncratic versions of a hoax.   Well the same idiosyncratic element exists among people that argue for the acceptance of the Apollo record.*  While we on this board are well united in our views, not everyone is.   Some are ignorant of physics, engineering and history. Maybe they are on their way to learning and are using the moon hoax debate as a tool for that.  Maybe they aren't.  Some are pretty much like the HBs, in that they want to get attentions and feel important with coup counting.  There are a number of sophomoric debates in my past too.  You have to start somewhere.  HBs will naturally respond to them because they deal on an emotional rather than technical level and can be relativity easy scores in the counting game, as illustrated in the example above.   

* I am thinking of our former member who accepted Apollo, chastised us for mistreating his friend, Jarrah White, and blasted at the Chinese space program as a hoax.  A very idiosyncratic view. 

[Luckmeister]

Also, isn't there radiation shielding in the helmet's clear visor and would that reduce some of the star luminosity?

[Allan F]

Also, isn't there radiation shielding in the helmet's clear visor and would that reduce some of the star luminosity?

There were a thin metallic coating (gold?) on the outermost visor, to keep out IR and visible ligth. They could (and did) raise the visor to get better view of things, since it was prone to scratching.

[JayUtah]

The LEVA visors were all prone to scratching.  The metallic gold coating on the Udel outer visor is meant to additionally attenuate visible light and reflect IR.  The inner Lexan visor was coated only for glare attenuation, on its inside surface.  Lexan is naturally opaque to UV.

No part of the EMU was meant to attenuate higher energy ionizing radiation to tolerable levels at anything above ambient incidence.  While some protection is afforded, it was largely incidental due simply to the bulk of material provided for other purposes such as micrometeoroid protection.

[AstroBrant]

I've discussed this with local HB's and I didn't have to backpedal. In daytime on Earth, scattering of sunlight in the atmosphere washes out the stars plus the eyes are not dark-adapted.

Both are true, but the fact that the eyes aren't dark adapted is irrelevant. During the daytime, if you used a camera on an exposure setting for stars, it would only make the sky appear much brighter. It wouldn't reveal stars. So saying, "You can't see stars on earth during the day," isn't equivalent to why you can't see them in space when the sun is shining.

Some have stated that they could see stars when the sun is up, but this is very rare and requires looking through a tube. Or it is done just as the sun is setting. They become more visible then because the sky is darkening, not because your eyes are becoming dark adapted. We can see the moon when the sun is shining, but that's because it's brighter than the ambient light in the atmosphere. Stars aren't.

On the Moon, reflected sunlight makes dark-adapting difficult and the astronauts were too busy to be stargazing even if they bothered to shield their eyes enough. In the ISS, interior lights will prevent dark-adapting. What's wrong with telling them that?

There's nothing wrong with them. Those are three good arguments -- ones I've used many times.

[Bryanpoprobson]

I've tried to keep Venus in view, as an experiment, when it is visible in the morning but it disappears, to the naked eye soon after sunrise. I have tracked it well into sunrise with a telescope though.

[Kiwi]

I've tried to keep Venus in view, as an experiment, when it is visible in the morning but it disappears, to the naked eye soon after sunrise.

Here in New Zealand it's usually no trouble to see Venus with the naked eye all day when it's at its brightest and close to maximum elongation from the Sun. Sometimes the hardest task is to find it, especially in summer when the atmosphere is a little hazier, but I do it the easy way by finding its exact azimuth and altitude from my astronomy program, then searching the area with binoculars. A polarising filter can also help by darkening the blue sky and making the faint white light of Venus a little more obvious.

I often point Venus out to people in the daytime by lining it up with two objects, and another good trick is note the days when the crescent moon is closest, then it's easiest to show others.

The first time I showed a group of people was at noon on 23 March 1990 when there were 70 high school kids at my local beach. The Moon and Venus were only 5.4° apart and Venus was 46.3° from the Sun and at magnitude -4.4, so it was quick and easy for the kids to find it.  From their comments, I don't think any of them knew Venus could be seen during the day.

[Glom]

I've tried to keep Venus in view, as an experiment, when it is visible in the morning but it disappears, to the naked eye soon after sunrise. I have tracked it well into sunrise with a telescope though.

Brave.

[Kiwi]

A request re. "Can you see stars in the daytime on earth?"

Yes, I agree that it's a good idea to drop that one, and have never used it.

However, when it comes to the claim that stars should have shown in the lunar surface photos, one thing that's underused in rebuttals is the number that disproves it.  People love numbers, and this one is a lovely big one with a few noughts or zeros:-- 30,000.

But that's just in theory. In practice, back in the days of film photography there was an even bigger number, 100,000.

Those are the differences between the correct exposure on film of sunlit scenes and the correct exposure on film of stars. Stars require at least 30,000 times and up to 100,000 times more exposure to register on film than a typical down-sun scene.

The full explanation is in a post of June 2003 at the Bad Astronomy Bulletin Board,
http://cosmoquest.org/forum/showthread.php/6040-Fox-Special-rescreening-in-NZ-24-June-2003?p=102903#post102903
but here are the details again:--

Should anyone think the figure regarding stars requiring "at least 30,000 times more exposure…." sounds much too high, here's the maths. A typical down-sun exposure with 100 ISO film is 1/250 at f11. The shortest exposure that will register the brightest stars is about 8 seconds at f2.8, but because of film's reciprocity failure during long exposures, 20 to 30 seconds at f2.8 is a better exposure.

 Each step below doubles the exposure and the increase over the sunlight exposure is shown.

 1/250 @ f11
 1/250 @ f8 ======= 2x
 1/250 @ f5.6 ====== 4x
 1/250 @ f4 ======= 8x
 1/250 @ f2.8 ===== 16x
 1/125 @ f2.8 ===== 32x
 1/60 @ f2.8 ====== 64x
 1/30 @ f2.8 ===== 128x
 1/15 @ f2.8 ===== 256x
 1/8 @ f2.8 ====== 512x
 1/4 @ f2.8 ===== 1,024x
 1/2 @ f2.8 ===== 2,048x
 1 sec @ f2.8 ==== 4,096x
 2 sec @ f2.8 ==== 8,192x
 4 sec @ f2.8 === 16,384x
 8 sec @ f2.8 === 32,768x
 16 sec @ f2.8 == 65,536x
 32 sec @ f2.8 = 131,072x